For example: Let's assume the sole information I have about a gentleman is that he is 40 years old, and I want to predict how long he will live. I can look at actuarial tables and find his age-adjusted life expectancy as used by insurance companies. The table will predict he has an extra 44 years to go; next year, when he turns 41, he will have a little more than 43 years to go.

For a perishable human, every year that elapses reduces his life expectancy by a little less than a year.

The opposite applies to non-perishables like technology and information. If a book has been in print for 40 years, I can expect it to be in print for at least another 40 years. But -- and this is the main difference -- if it survives another decade, then it will be expected to be in print another 50 years.